CN110382819B

CN110382819B - Buffer tool for downhole tool string

Info

Publication number: CN110382819B
Application number: CN201780086051.2A
Authority: CN
Inventors: 迈克尔·R·布朗
Original assignee: Lord Corp
Current assignee: Lord Corp
Priority date: 2016-12-12
Filing date: 2017-12-12
Publication date: 2022-09-06
Anticipated expiration: 2037-12-12
Also published as: EP3551848B1; US20190338631A1; US11008852B2; EP3551848A2; CA3046494C; WO2018111863A3; WO2018111863A2; CN110382819A; CA3046494A1

Abstract

The snubber tool may be installed in a downhole tool string to reduce vibration in the downhole tool string. The snubber tool includes a drive washer that selectively applies further compression to the compliance member in response to an external force acting on the snubber tool and two compliance members having different stiffness characteristics and precompression. The compliance member maintains its initial precompression under the external load of the damper tool.

Description

Buffer tool for downhole tool string

Cross Reference to Related Applications

The present application claims priority from us provisional patent application 62/432,743 entitled "buffer tool for a downhole tool string" filed on 12/2017, which is incorporated herein by reference.

Background

Universal bottom hole directional ("UBHO") subs are commonly used in directional drilling Bottom Hole Assemblies (BHAs). The UBHO joints have a hollow cylindrical inner member called a "mule shoe" or "landing sleeve". A directional measurement tool, such as a Measurement While Drilling (MWD) tool or a Logging While Drilling (LWD) tool, may be contained within and locked to the mule shoe. The orientation measurement tool may include electronics and/or other sensitive hardware. During drilling, the tool string will be subjected to considerable vibrations. To prevent damage to sensitive parts of the orientation measurement tool, the sensitive parts may be enclosed in an anti-vibration housing. However, in some cases, the vibration-proof housing may not provide sufficient protection for sensitive components. In some cases, it may be desirable to use an isolation system to protect sensitive components from harmful vibrations, for example, vibrations at a certain frequency.

International publication WO 2015/112821(Cune et al) describes an isolation mule shoe that can provide the functionality of a conventional mule shoe while protecting sensitive components from vibrations, for example, at frequencies between 110Hz and 200 Hz. An isolating mule shoe includes an isolator module having at least two axial displacement elements that are axially movable to shorten or lengthen the isolator in response to vibration and/or shock input to the isolator.

Disclosure of Invention

In some embodiments of the present disclosure, a bumper tool for a downhole tool string includes a mule shoe adapter and a UBHO adapter for mounting the bumper tool in the downhole tool string. The buffer tool further comprises: a resilient compliance member having a first stiffness and a first precompression; and a compression compliance member having a second stiffness greater than the first stiffness and a second precompression less than the first precompression. The rebound compliance component and the compression compliance component are configured to maintain at least a portion of the first precompression and the second precompression, respectively, under an external load of the bumper tool. The damper unit may further include a drive washer disposed between the resilient compliance member and the compressive compliance member and coupled to the mule shoe adapter. The drive washer may be configured to selectively apply further compression to the resilient and compressive compliance members in response to a force acting on the mule shoe adapter.

In some embodiments of the present disclosure, a downhole tool string comprises: a UBHO fitting having a mule shoe disposed therein; and a buffer tool as described above disposed within the UBHO joint. A mule shoe adapter of the buffer tool is coupled to the mule shoe and a UBHO adapter of the buffer tool is mounted to the UBHO fitting.

In other embodiments of the present disclosure, a method of reducing vibration in a downhole tool string having a mule shoe includes installing a snubber tool as described above in the downhole tool string. The installing may include coupling the buffer tool to a mule shoe of the downhole tool string. The method comprises the following steps: receiving a force exerted on the mule shoe at the drive washer of the snubber tool; and further compressing one of the rebound compliance component and the compression compliance component of the damper tool by movement of the drive washer in response to the received force.

The foregoing general description and the following detailed description are exemplary of the invention and are intended to provide an overview or framework for understanding the nature of the invention as it is claimed. The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate various embodiments of the invention and together with the description serve to explain the principles and operations of the invention.

Drawings

FIG. 1A is a cross-sectional view of a bumper tool for a downhole tool string in an assembled state.

FIG. 1B is a cross-sectional view of FIG. 1A taken along line 1B-1B.

Fig. 2 is a schematic view of a mule shoe adapter.

Fig. 3 is a schematic diagram of a UBHO adapter.

Fig. 4A is a cross-sectional view of a resilient compliance element.

Figure 4B is a cross-sectional view of a resiliently compliant component of a stack including a resiliently compliant element.

Fig. 5A is a cross-sectional view of a compression compliance element.

Fig. 5B is a cross-sectional view of a compression compliance component of a stack including a compression compliance element.

Fig. 6A is a schematic view of a drive washer.

FIG. 6B is an enlarged cross-sectional view of the bumper tool of FIG. 1A prior to pre-compression, and FIG. 6B focuses on the area containing the drive washer.

FIG. 7A is an enlarged cross-sectional view of the bumper tool of FIG. 1A prior to pre-compression, and FIG. 7A focuses on the area containing the resiliently compliant member.

FIG. 7B is an enlarged cross-sectional view of the bumper tool of FIG. 1A in an assembled state, and FIG. 7B focuses on the area containing the resiliently compliant component.

FIG. 8 is a load deflection plot of an exemplary configuration of the bumper tool of FIG. 1A.

Fig. 9 is a cross-sectional view of a bumper tool disposed inside a UBHO fitting and assembled to a mule shoe.

Detailed Description

Bumper tools for downhole tool strings (e.g., MWD tool strings, etc.) protect the electronics and other sensitive equipment within the tool string from repeated vibrations and shock vibrations. In some cases, the buffer tool has an adapter that enables the buffer tool to be disposed within and coupled to a mule shoe of the UBHO joint. The snubber tool is designed to mitigate the shock transmitted along the pipe string. According to some embodiments, the damper means may have a natural frequency of 80Hz or higher and may be configured to isolate the vibration sensitive component from vibration frequencies of 200Hz or higher. In some embodiments, the snubber tool uses an elastomeric portion that is always in compression regardless of whether a net compressive load or a net tensile load is applied to the snubber tool. This allows for extended life and soft damping of the downhole elastomer components when the bumper tool is in overall compression or tension.

Fig. 1A shows a cross-sectional view of a buffer tool 100, the buffer tool 100 including a mule shoe adapter 200, a UBHO adapter 300, and a buffer unit 400. The damper unit 400 includes a damper housing 402, a rebound compliance member 408, a drive washer 410, and a compression compliance member 412. The buffer tool 100 may have an axial axis 102, with the mule shoe adapter 200, the UBHO adapter 300, and the buffer unit 400 being substantially axially aligned along the axial axis 102. In some embodiments, mule shoe adapter 200 enables buffer tool 100 to be coupled to a conventional mule shoe/landing sleeve (not shown), and UBHO adapter 300 enables buffer tool 100 to be installed within a conventional UBHO (not shown).

Fig. 2 shows a schematic view of a mule shoe adapter 200. Referring to fig. 1A and 2, the mule shoe adapter 200 may have an adapter head 202 and an adapter body 204. The adapter body 204 is adapted to be inserted into and coupled to the buffer unit 400, while the adapter head 202 is adapted to be coupled to another tool component, such as a mule shoe/landing sleeve (not shown). The mule shoe adapter 200 has a central bore 206, the central bore 206 extending through the adapter head 202 and the adapter body 204. The inner surface 208 of the adapter head 202 may include threads 209, the threads 209 for forming a threaded connection with another tool member, such as a mule shoe/landing sleeve (not shown). The outer surface 210 of the adapter head 202 may include a circumferential recess 212. The outer wear strips 214 may be disposed in the circumferential recess 212. The outer wear strips 214 may provide lubrication and sliding support when the outer surface 210 is mated with another surface (not shown) or used as a bearing surface.

The adapter body 204 may include, in order, an upper body portion 216, a threaded body portion 218, a tapered body portion 220, and a lower body portion 222. The upper body portion 216 may have a large diameter portion 216A and a small diameter portion 216B. Referring to fig. 2, a pocket 224 is formed in an outer surface 225 of the large diameter portion 216A of the upper body portion 216. In some examples, the pockets 224 may be distributed around the circumference of the large diameter portion 216A and may be shaped to receive anti-rotation pins. FIG. 1A (as well as FIG. 1B) shows an anti-rotation pin 227 in the pocket 224. In some embodiments, the pocket 224 is longer (in the axial direction 102) than the anti-rotation pin 227 such that the anti-rotation pin 227 is allowed to move axially within the pocket 224. Anti-rotation pins 227 may be used to prevent rotation of mule shoe adapter 200 relative to buffer unit 400 while allowing axial movement of mule shoe adapter 200 relative to buffer unit 400. Other structures besides anti-rotation pins, such as multi-sided splines and convoluted ridges, may also be used to prevent rotation of the mule shoe adapter 200 relative to the buffer unit 400. In this case, splines may be formed on the upper body portion 216 rather than pockets for receiving anti-rotation pins.

Returning to fig. 2, a groove 226 is formed in the outer surface 225 of the large diameter portion 216A of the upper body portion 216. In some examples, the grooves 226 may be distributed around the circumference of the large diameter portion 216A and may alternate with the pockets 224. In some examples, the groove 226 is oriented substantially parallel to an axial axis 229 of the mule shoe adapter 200. The groove 226 provides a flow path or pressure port on the upper body portion 216 and may prevent or reduce wear or washout of the outer surface 225 of the upper body portion 216 and any mating surfaces due to high velocity flow.

Returning to FIG. 1A, the threaded body portion 218 has an outer surface 230 with threads 232 formed on the outer surface 230. The threads 232 may be used to form a threaded connection between the mule shoe adapter body 204 and the drive washer 410 of the buffer unit 400. The tapered body portion 220 adjacent the threaded body 218 has a tapered outer surface 233. The tapered outer surface 233 tapers in a direction from the threaded body portion 218 to the lower body portion 222, or the outer diameter of the tapered body portion 220 decreases in a direction from the threaded body portion 218 to the lower body portion 222. In some embodiments, the taper angle of the tapered outer surface 233 can be about 6 degrees per side or include about 12 degrees.

Fig. 3 shows a schematic diagram of a UBHO adapter 300. Referring to fig. 1A and 3, UBHO adapter 300 has a small outer diameter portion 302 and a large outer diameter portion 304. UBHO adapter 300 has a central bore 306, central bore 306 extending through small outer diameter portion 302 and large outer diameter portion 304. The central bore 306 may be generally cylindrical in shape. In some examples, the inner diameter of the small outer diameter portion 302 is selected such that the lower body portion 222 of the mule shoe adapter body 204 can be at least partially received within the central bore 306. The inner diameter of small outer diameter portion 302 may be such that an inner surface 308 (in fig. 1A) of UBHO adapter small outer diameter portion 302 mates with an outer surface 234 of mule shoe adapter body portion 204. In this mated position, the central bore 206 of mule shoe adapter 200 and the central bore 306 of UBHO adapter 300 are aligned to form a central passage through the buffer tool 100 for fluids and tools.

In some examples, inner surface 308 of UBHO small outer diameter portion 302 may include a circumferential recess 310 with wear strips 312 mounted in circumferential recess 310. The wear strip 312 may provide lubrication between the mating mule shoe adapter surface 234 and the UBHO adapter surface 308. The wear strips 312 may further assist in aligning the mule shoe adapter 200 and the UBHO adapter 300 along the axial axis 102 of the bumper tool 100.

In some examples, the threads 314 can be formed on an outer surface 316 of the small outer diameter portion 302. The threads 314 may be used to form a threaded connection with the damper housing 402 of the damper unit 400.

In some examples, the O-ring 318 may be disposed in a groove 320 in an outer surface 322 of the large outer diameter portion 304. O-ring 318 may seal between UBHO adapter 300 and another tool component (e.g., a UBHO sub).

Referring to fig. 1A, the buffer housing 402 of the buffer unit 400 may be in the form of a sleeve. The O-ring 401 may be disposed in a groove in the outer surface of the housing 402. An O-ring 401 may seal between the bumper housing 402 and the mating surface of another tool member. For example, O-ring 401 may seal between mating surfaces of bumper housing 402 and a UBHO joint when bumper tool 100 is disposed in a UBHO joint (not shown). The damper housing 402 has an inner surface 407, the inner surface 407 defining a generally cylindrical bore 404, the bore 404 being alignable along the axis 102. In some examples, the threads 405 may be formed on a lower portion of the inner surface 407 of the bumper housing 402. Fig. 1A shows upper body portion 302 of UBHO adapter 300 inserted into the lower portion of hole 404. Additionally, a threaded connection 409 is formed between the internal threads 405 of the bumper housing 402 and the external threads 314 of the UBHO adapter 300.

Fig. 1A also shows the mule shoe adapter body 204 occupying a central portion of the bore 404. In some embodiments, an anti-rotation pin 227 is inserted between the mule shoe adapter body 204 and the damper housing 402 to prevent the mule shoe adapter 200 from rotating relative to the damper housing 402. Referring to fig. 1B, a groove 411 is formed on the inner surface 407 of the bumper housing 402. The recess 411 on the inner surface 407 of the bumper housing 402 corresponds to the pocket 224 on the outer surface 225 of the mule shoe adapter body 204. Prior to inserting the mule shoe adapter body 204 into the bumper housing 402, the anti-rotation pins 227 are disposed in the pockets 224 on the outer surface 225 of the mule shoe adapter body 204. The pockets 224 are sized relative to the anti-rotation pins 227 so that an outer portion of the anti-rotation pins 227 protrude from their corresponding pockets 224. When the mule shoe adapter body 204 is inserted into the bumper housing 402 and the recesses 411 are aligned with the pockets 224, these protruding outer portions of the anti-rotation pins 227 slide into the corresponding recesses 411. The mule shoe adapter 200 is allowed to move axially relative to the draft gear housing 402 by an anti-rotation pin 227 disposed between the pocket 224 and the recess 411, but the mule shoe adapter 200 is prevented from rotating relative to the draft gear housing 402.

Returning to fig. 1A, the resilient compliance member 408, the drive washer 410, and the compression compliance member 412 of the damper unit 400 are stacked in the annular space 406 between the mule shoe adapter body 204 and the damper housing 402. Each of the resilient compliance member 408, the drive washer 410, and the compressive compliance member 412 surrounds a portion of the mule shoe adapter body 204. In some examples, a drive washer 410 is mounted between and in contact with both the resilient compliance member 408 and the compressive compliance member 412 such that the drive washer 410 can apply axial compression to either of the

members

408, 412 in response to an external force. In some embodiments, shelves 403 are formed on an inner surface 407 of the damper housing 402, and the resilient compliance member 408 is pre-compressed between the damper housing shelves 403 and the drive washer 410. Additionally, compression compliance member 412 is pre-compressed between drive washer 410 and UBHO adapter end face 324.

The resilient compliance member 408 in fig. 1A may include two or more resilient compliance elements. Fig. 4A shows a cross-section of an exemplary resiliently compliant element 420, the resiliently compliant element 420 comprising shims (or spacer rings) 424, 426 arranged in parallel. Elastomeric ring 430 is sandwiched between

shims

424, 426. The

spacers

424, 426 may be made of metal, alloy or plastic. Elastomeric ring 430 may be bonded to

shims

424, 426 to form a unitary structure. Inner surface 431 of elastomeric ring 430 and

inner surfaces

425, 427 of

shims

424, 426, respectively, may form central opening 429. The central opening 429 allows the resilient compliance member 408 to fit around a portion of the mule shoe adapter body (204 in fig. 1A).

Elastomeric ring 430 has an axial thickness 430W and a radial thickness 430T. In some examples, radial thickness 430T may be selected to be less than thickness 424T of shim 424 (or shim 426) such that a peripheral surface of elastomeric ring 430 is recessed relative to respective

peripheral surfaces

434, 436 of

shims

424, 426. In some examples, outer peripheral surface 432 of elastomeric ring 430 may have a contoured profile in a relaxed state. The contoured profile may be selected to reduce induced strain in elastomeric ring 430 when elastomeric ring 430 is compressed. The contoured profile may be defined by a curved profile or a combination of a curved profile and a flat profile. In some cases, the contoured profile may be such that circumferential surface 432 has a generally concave shape in the relaxed state. In some examples, although not shown, inner surface 431 of elastomeric ring 430 may also be contoured.

When elastomeric ring 430 is subjected to a large load (bulk loading), outer surface 432 and inner surface 431 will bulge, i.e., expand radially. Where the surface has a contour, when elastomeric ring 430 is convex, the contour profile can be determined by a desired form factor, where the form factor can be determined by the ratio of the bearing area to the convex area of the elastomer.

As previously described, the resilient compliance member 408 may have two or more resilient compliance elements. Fig. 4B shows a cross-section of a resiliently compliant component 408, the resiliently compliant component 408 comprising a stack of two compliance elements 420 (identified as 420A, 420B, respectively). In this stack, the bottom shim 426A of the upper compliance member 420A may simultaneously serve as the top shim of the lower compliance member 420B. The bottom shim 426A will then act as a spacer between adjacent

elastomeric rings

430A, 430B in the stack. Thus, a resiliently compliant component may be generally described as a structure comprising a stack of elastomeric rings interleaved with non-elastomeric shims, or comprising a stack of alternating elastomeric rings and non-elastomeric shims, wherein the elastomeric rings are configured to provide a predetermined contribution of the resiliently compliant component to the desired axial stiffness of the compliant isolator. Typically, the elastomeric rings in the stack are the same, but it is also possible to use different elastomeric rings in the stack, for example elastomeric rings having different axial or radial thicknesses.

To prevent metal-to-metal contact when the resilient compliance member 408 is installed around the mule shoe adapter body (204 in fig. 1A) and the damper tool (100 in fig. 1A) is in an assembled state, the outer diameter of the elastomer rings 430A, 430B of the resilient compliance member 408 may be selected to be smaller than the inner diameter of the damper housing (402 in fig. 1A) so that there is a small gap between the elastomer rings of the resilient compliance member 408 and the damper housing 402. Such a gap is shown, for example, at 433 in fig. 6B. The gap, which may be referred to as a buffer gap, may have a minimum of 0.01 inches in some cases.

The compression compliance component (412 in fig. 1A) may include two or more compression compliance elements. Fig. 5A illustrates a cross-sectional view of an exemplary compression compliance element 440, the compression compliance element 440 may have a structure similar to that of the rebound compliance element 420. The compression compliance element 440 may include shims (or spacer rings) 444, 446 arranged in parallel. Elastomeric ring 450 is sandwiched between

shims

444, 446, which shims 444, 446 may be made of, for example, metal, alloy, or plastic. Elastomeric ring 450 may be bonded to

shims

444, 446 to form a unitary structure. The inner surface 451 of the elastomeric ring 450 and the

inner surfaces

445, 447 of the

shims

444, 446, respectively, may form a central opening 449 that allows the compression compliance element to be mounted on the lower body portion of the mule shoe adapter body (204 in fig. 1A).

Elastomeric ring 450 has an axial thickness 450W and a radial thickness 450T. As previously described, the structure of the compression compliance member 440 may be similar to the structure of the rebound compliance member (420 in FIG. 4A). However, one significant difference between the compression compliance component 440 and the rebound compliance component (420 in FIG. 4A) is that the axial thickness 450W of the compression elastomer ring 450 is relatively less than the axial thickness (430W in FIG. 4A) of the rebound elastomer ring (430 in FIG. 4A). This generally means that the compression compliance member is relatively stiffer than the rebound compliance member, or the rebound compliance member is relatively more flexible than the compression compliance member.

In some examples, the radial thickness 450T may be selected to be less than the thickness 444T of the shim 444 (or the shim 446) such that the outer peripheral surface 452 of the elastomeric ring 450 is recessed relative to the respective outer

peripheral surfaces

454, 456 of the

shims

444, 446. Generally, the amount of concavity will be determined by the expected bulge of the elastomeric ring 450 under high load. Under large loads, the elastomeric ring 450 will fill any available free volume between the elastomeric ring and the adjacent surfaces of the mule shoe adapter body (204 in fig. 1A) and the damper housing (402 in fig. 1A). In other examples, radial thickness 450T may be substantially the same as thickness 444T of the shim.

In some cases, the outer circumferential surface 452 of the elastomeric ring 450 may have a contoured profile in a relaxed state, and the contoured profile may be selected to reduce induced strain in the elastomeric ring 450 when the elastomeric ring 450 is compressed. The contoured profile may be defined by a curved profile or a combination of a curved profile and a flat profile. In some cases, the contoured profile may be such that the circumferential surface 452 has a generally concave shape. When elastomeric ring 450 is compressed, outer circumferential surface 452 will bulge or radially expand. When elastomeric ring 450 is compressed, the contoured profile of outer peripheral surface 452 may be determined based on a desired form factor. Although not shown, the inner surface 451 of the elastomeric ring may also be shaped in the manner of the outer surface 452 described above.

As previously described, the compression compliance component (412 in fig. 1A) may have two or more compression compliance elements. Fig. 5B illustrates one embodiment of a compression compliance member 412, the compression compliance member 412 including a stack of three compression compliance elements 440 (identified as 440A, 440B, 440C, respectively). In this stack, the bottom shim 446A of the upper compression compliance element 440A may simultaneously serve as the top shim of the intermediate compression compliance element 440B, and the bottom shim 446B may simultaneously serve as the top shim of the bottom compression compliance element 440C. In this case, the bottom shims 446A, 446B serve as spacers between the

elastomeric rings

450A and 450B and between 450B and 450C, respectively, in the stack. Thus, the compression compliance component may generally be described as a structure comprising a stack of elastomeric rings interleaved with non-elastomeric shims, or comprising a stack of elastomeric rings and non-elastomeric shims arranged alternately, wherein the elastomeric rings are configured to provide a predetermined contribution of the compression compliance component to the desired axial stiffness of the compliance isolator. Typically, the elastomeric rings in the stack are the same, but it is also possible to use different elastomeric rings in the stack, for example elastomeric rings having different axial and radial thicknesses.

To prevent metal-to-metal contact when the compression compliance component 412 is installed around the mule shoe adapter body (204 in fig. 1A) and the bumper tool (100 in fig. 1A) is in an assembled state, the outer diameter of the elastomeric rings 450A, 450B, 450C of the compression compliance component 412 may be selected to be less than the inner diameter of the bumper housing (402 in fig. 1A) such that there is a small gap between the elastomeric rings of the compression compliance component 412 and the bumper housing 402. Such a gap is shown, for example, at 453 in FIG. 6B. The gap, which may be referred to as a buffer gap, may have a minimum of 0.01 inches in some cases.

Returning to FIG. 1A, as described above, the structure of the resilient compliance member 408 may be similar to the structure of the compression compliance member 412. However, the resilient compliance member 408 may be distinguished from the compressive compliance member 412 by its stiffness. Generally, the resiliently compliant member 408 will be relatively softer than the compressively compliant member 412, or the compressively compliant member 412 will be relatively harder than the resiliently compliant member 408. This may be observed in the amount of pre-compression each component may take during assembly of the buffer tool. Generally, the resilient compliance member 408 will have a much higher pre-compression deformation than the compression compliance member 412. The resilient compliance member 408 may also be distinguished from the compressive compliance member 412 by the axial thickness of the elastomeric ring. Generally, the sum of the axial thicknesses of the elastomeric rings in the resilient compliance component 408 will be greater than the sum of the axial thicknesses of the elastomeric rings in the compression compliance component 412. The resilient compliance member 408 is configured to withstand a resilient load. That is, as tension is applied to the bumper tool, the resilient compliance member 408 will compress further. On the other hand, the compression compliance component 410 is configured to withstand static loads due to gravity and dynamic loads when the bumper tool 100 is compressed.

Fig. 6A shows a schematic view of the drive washer 410. Fig. 6B is an enlarged cross-sectional view of the bumper tool 100 shown in fig. 1A, with fig. 6B focusing on the area containing the drive washer 410. Referring to fig. 6A and 6B, the drive washer 410 includes a cylindrical body 470 and an inner surface 472, the inner surface 472 defining a central opening 473. Threads 474 are formed on the upper portion 472A of the inner surface 472. The drive washer threads 474 engage the mule shoe adapter threads 232 to form a threaded connection 476 (in fig. 6B) between the drive washer 410 and the mule shoe adapter body 204. The lower portion 472B of the inner surface 472 is tapered. The taper angle of the tapered inner surface 472B is selected to match the taper angle of the tapered outer surface 233 of the mule shoe adapter body 204. The drive washer 410 is designed such that higher compression/impact loads will react through the taper angle of the tapered inner surface 472B rather than only acting on the threads 474. The tensile resilient load is reacted solely by threads 474. The threads 474 will also carry a mounting load. In some cases, the threads 474 may carry a makeup load of 20,000lbf to 75,000 lbf.

Referring to fig. 6A, in some examples, a slot 478 can be formed in an end 480 of the cylindrical body 470. The slots 478 may be distributed along the circumference of the cylindrical body 470. The slot 478 has a base 482, and the base 482 may be angled, as shown, or flat. The slot 478 may serve as an adjustable wrench slot for assembly and disassembly purposes. A through hole 484 is formed in the wall of the cylindrical body 470. The aperture 484 may extend from the base 482 of the slot 478 to a counterbore 485 (in fig. 6B) on the end face 483 (in fig. 6B) of the cylindrical body 470. The aperture 484 may serve as a pressure compensation port. In some examples, the aperture 484 allows fluid communication between an inner surface of the resilient compliance component 408 (i.e., the surface opposite the mule shoe adapter body 204) and an inner surface of the compression compliance component 412 (i.e., the surface opposite the mule shoe adapter body 204). The aperture 484 also allows fluid communication between the outer surface of the rebound compliance member 408 (i.e., the surface opposite the damper housing 402) and the outer surface of the compression compliance member 412 (i.e., the surface opposite the damper housing 402).

Returning to FIG. 1A, in the assembled state of the buffer tool 100, the buffer tool 100 is pre-compressed. That is, the resilient compliance member 408 and the compressive compliance member 412 (or more specifically, the elastomeric rings of the compliance members 408, 412) are precompressed. Pre-compression may be achieved during assembly of the buffer tool. One method of pre-compression may include compressing a "buffer stack" that includes a resilient compliance member 408, a drive washer 410, and a compressive compliance member 412 between the shelf 403 of the buffer housing 402 and the end face 324 of the UBHO adapter 300. The term "compress the buffer stack" is used because the initial length of the buffer stack prior to pre-compression will be longer than the distance between the buffer housing shelf 403 and the UBHO adapter end face 324 measured in the direction of the axis 102. Thus, pre-compression in the resilient compliance member 408 and the compressive compliance member 412 is achieved by shortening the length of the stack and constraining the stack between the shelf 403 and the end face 324. It should be noted that the drive washer 410 is non-elastic such that pre-compression occurs in the

compliance members

408, 412. The method of pre-compression may include mounting the resilient compliance member 408, the drive washer 410, and the compression compliance member 412 on the mule shoe adapter body 204. An anti-rotation pin 227 may also be disposed in the pocket 224 on the mule shoe adapter body 204. The mule shoe adapter body 204 is then inserted into the bumper housing 402. This may include sliding the anti-rotation pin 227 into a recess 411 in the bumper housing 402. Finally, threads 314 of

UBHO adapter

300 and 405 of buffer housing 402 are respectively threaded until end face 324 of UBHO adapter 300 contacts compression compliance 412. The

threads

314, 405 are further threaded to compress the buffer stack and achieve the desired precompression of the

compliance members

408, 412. Fig. 7A illustrates a portion of the damper tool 100 including a resilient compliance member 408 prior to precompression. The elastomeric ring 430 of the resilient compliance member 408 is in a relaxed state and the upper end of the resilient compliance member 408 is not engaged with the shelf 403 of the damper housing 402. FIG. 7B shows the same portion of the bumper tool of FIG. 7A after pre-compression. Due to the pre-compression, the upper end of the resilient compliance member 408 has moved along the mule shoe adapter body 204 and engaged the damper housing shelf 430, and the elastomer ring 430 of the resilient compliance member 408 is now convex. However, there are still

gaps

500, 502 between the elastomeric ring 430 and the adjacent respective surfaces of the damper housing 402 and the mule shoe adapter body 204. These voids will be filled when the resilient compliance member 408 is further compressed due to tension or large loads on the bumper tool. The compression compliance member (412 in FIG. 1A) is precompressed in the same manner as the rebound compliance member, and the void around the elastomer ring is filled during the application of a large load to the compression compliance member.

Returning to fig. 1A, in some examples, a minimum combined precompression of 0.2 inches is applied to the resilient compliance member 408 and the compression compliance member 412. Generally, as precompression increases, the axial stiffness of the bumper tool 100 will increase. The precompression will be divided between the rebound compliance member 408 and the compression compliance member 412 with the rebound compliance member 408 taking up the majority of the precompression. For example, in some cases, the resilient compliance member 408 may account for 90% or more of the precompression, with the remainder of the precompression occurring in the compression compliance member 412. The pre-compression will ensure that there is no clearance between the elastomeric rings of the

compliance members

408, 412 and the shelf 403 of the housing unit and the end face 234 of the UBHO adapter 300 when a load is transferred to the damper tool 100. This will have the following effect: providing better fatigue life for the elastomer, and damping under both rebound and compression loads.

In some embodiments, a shock absorber configured to have an axial stiffness of 80,000lb/in at 850lbf includes a rebound compliance member 408 having two rebound compliance elements and a compression compliance member 412 having three rebound compliance elements. Each resiliently compliant element comprises an elastomeric ring having an axial thickness of 0.36in +/-0.004 in. Each compression compliance element comprises an elastomeric ring having an axial thickness of 0.08in +/-0.004 in. The bumper tool 100 is pre-compressed by about 0.2 inches. This means that the rebound compliance member and the compression compliance member are pre-compressed by about 0.2 inches, with the rebound compliance member 408 occupying the majority of the pre-compression, e.g., about 0.195 inches, and the compression compliance member occupying the remaining pre-compression, e.g., about 0.005 inches. Typically, the damper tool 100 may be precompressed by a minimum of 0.2 inches, with the resilient compliance member 408 occupying a majority of the precompression. For the configuration where the damper tool 100 is pre-compressed 0.2 inches, soft damping (i.e., the non-linear viscoelastic behavior of the elastomer) begins to occur at 0.02 inches of deformation and large loads occur between 0.05 inches and 0.1 inches. The high load refers to the elastomer ring filling the adjacent void in the annular space between the mule shoe adapter and the damper housing. FIG. 8 shows a load deflection curve 150 for the bumper tool 100 constructed as described above (i.e., with 0.2 inches of precompression). Horizontal line 152 represents 850lbf, which is the load for which stiffness is measured. 0 inches to 0.02 inches is a linear range of bumper tool stiffness. 0.02 inches to 0.05 inches is the "soft cushioning" range for the cushion tool. Above 0.05 inches is the "heavy load" range for the bumper tool. Due to the thickness of the

compliance member

408, 412 and the deformation required to put the damper tool into heavy loading, the damper tool will not lose its initial precompression. Thus, once the buffer tool is set (keys on set) due to higher temperatures (e.g., 300 ° F to 350 ° F) and loaded for a long time in operation, the buffer tool will enter a heavy load condition without losing pre-compression. Generally, the thickness and precompression of the

compliance member

408, 412 are selected so that the

compliance member

408, 412 does not lose precompression when the damper tool enters a high load condition.

Fig. 9 shows a cross-sectional view of a UBHO joint 600 with a mule shoe 602. Mule shoe 602 is a hollow cylindrical inner member of UBHO joint 600 and may also be referred to as a landing sleeve. The orientation measurement tool 604 is locked into the mule shoe 602. The orientation measurement tool 604 may include a pulser screw interface 612, a wear collar 614, an alignment key 616, and a bottom sleeve 618. Although not shown, the bottom sleeve 618 may contain sensitive components that need to be isolated from vibrations at a selected frequency. Further, other components may be coupled to the orientation measurement tool 604 and the UBHO joint 600 that need to be isolated from vibrations at selected frequencies. The buffer tool 100 is disposed within the UBHO sub 600. In some cases, UBHO joint 600 may include a seat 620, with UBHO adapter 300 of buffer tool 100 mounted on seat 620. UBHO adapter 300 may then be secured to the body of UBHO joint 600 by inserting set screws (not shown) into holes 622 in UBHO joint 600. Holes 622 may be distributed around the circumference of UBHO joint 600. The setscrews will extend to a circumferential recessed surface 326 (see also fig. 3) on UHBO adapter 300 and engage UBHO adapter 300. Other methods of fixing the UBHO adapter 300 to the UBHO joint may be used in addition to the above-described methods. For example, the mule shoe adapter head 202 of the buffer tool 100 may be coupled to the bottom sleeve 618 by making a threaded connection 606 between the mule shoe adapter head 202 and the bottom sleeve 618.

In operation, the damper tool 100 may receive a perturbed axial input force (e.g., a compressive force and/or a tensile force) from the mule shoe 602. The force may be transferred to the mule shoe adapter 200 and then to the drive washer 410. Referring to FIG. 1A, in response, the drive washer 410 will move axially within the annular space 406, thereby further compressing either the rebound compliance member 408 or the compression compliance member 412. Under the compressive load of the damper tool 100, the drive washer 410 will further compress the compression compliance member 412, thereby releasing the compression from the rebound compliance member 408. Under the tensile load of the damper tool 100, the drive washer 410 will further compress the resilient compliance member 408, thereby releasing the compression from the compression compliance member 412. It should be noted that the resilient compliance member 408 and the compression compliance member 412 are always maintained in a pre-compressed state, i.e., whether the damper tool 100 is in overall compression or tension. Generally, the drive washer 410 will act as a piston within the annular space 406, moving against either the rebound compliance member 408 or the compression compliance member 412 in response to an external load on the damper tool 100. The elastomeric ring of the

compliance member

408, 412 is configured to bulge, i.e., radially expand, to fill the entire "free volume" between the outer diameter of the elastomeric ring and the inner diameter of the damper housing 402/outer diameter of the mule shoe adapter body 204. If the shock/vibration event is large enough for it to occur, the bumper tool 100 will go into "heavy load". For example, as shown in fig. 8, soft cushioning (i.e., the non-linear viscoelastic behavior of an elastomer) can also occur. Damping is enhanced during soft cushioning.

The design of buffer tool 100 allows it to be used in UBHO joints of various sizes without changing the internal structure of the tool. Typically, the only changes required when using the buffer tool for different sizes of UBHO are adjusting the wall thickness of the buffer housing 402, the wall thickness of the lower body portion 304 of the UBHO adapter 300, the wall thickness of the mule shoe adapter head 202.

After running the snubber tool 100 downhole, the replaceable components of the snubber tool 100 will be the rebound compliance component 408, the compression compliance component 412, the anti-rotation pin 227, the wear strips 214, 312, and the O-ring 318. All major metal components of the bumper tool 100 will be reusable, making the bumper tool 100 a cost effective tool for downhole use.

While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as disclosed herein. Accordingly, the scope of the invention should be limited only by the attached claims.

Claims

1. A bumper tool for a downhole tool string, the bumper tool comprising:

a mule shoe adapter;

a universal downhole orientation (UBHO) adapter;

a rebound compliance component having a first stiffness and a first precompression, the rebound compliance component configured to maintain at least a portion of the first precompression under an external load of the bumper tool;

a compression compliance component having a second stiffness greater than the first stiffness and a second precompression less than the first precompression, the compression compliance component configured to maintain at least a portion of the second precompression under an external load of the bumper tool; and

a drive washer disposed between, in contact with, and coupled to the mule shoe adapter, the resilient compliance component and the compressive compliance component, the drive washer configured to selectively apply further compression to the resilient compliance component and the compressive compliance component in response to an external force acting on the mule shoe adapter.

2. The cushion tool of claim 1, wherein the resilient compliance component and the compression compliance component are configured to maintain the first pre-compression and the second pre-compression, respectively, under a large load of the cushion tool.

3. The bumper tool of claim 1, further comprising a housing having an aperture,

wherein the mule shoe adapter has a mule shoe adapter portion received within the bore, and

the resilient compliance member, the compressive compliance member, and the drive washer are arranged in a stack in an annular space between the mule shoe adapter portion and the housing.

4. The buffer tool of claim 3, wherein the Universal Bottom Hole Orientation (UBHO) adapter has a Universal Bottom Hole Orientation (UBHO) adapter portion received within the bore and secured to the housing.

5. The snubber tool of claim 4, wherein the rebound compliance component, the drive washer, and the compression compliance component are compressed between an end face of the universal downhole orientation (UBHO) adapter portion and a shelf formed on an inner surface of the housing, a distance between the shelf and the end face being selected to cause the first and second precompression in the rebound compliance component and the compression compliance component, respectively.

6. The snubber tool of claim 5, wherein the universal downhole orientation (UBHO) adapter portion includes an external threaded surface, the housing includes an internal threaded surface, and the universal downhole orientation (UBHO) adapter and the housing are configured such that engagement of the external threaded surface with the internal threaded surface applies the first pre-compression to the rebound compliance component and the second pre-compression to the compression compliance component.

7. The buffer tool of claim 5, wherein an end of the mule shoe adapter portion is received within a bore of the universal downhole orientation (UBHO) adapter such that an outer surface portion of the mule shoe adapter portion mates with an inner surface portion of the universal downhole orientation (UBHO) adapter portion, and further comprising a wear resistant band disposed between the mating outer surface portion and the inner surface portion.

8. The buffer tool of claim 5, further comprising a plurality of anti-rotation pins interposed between the mule shoe adapter portion and the housing for preventing rotation of the mule shoe adapter relative to the housing.

9. The bumper tool of claim 1, wherein the mule shoe adapter comprises an internally threaded surface adapted to engage an externally threaded surface of a sleeve of the downhole tool string.

10. The cushion tool of claim 3, wherein the resilient compliance component comprises a first stack of at least two first elastomeric rings and the compressive compliance component comprises a second stack of at least two second elastomeric rings.

11. The buffer tool of claim 10, wherein a combined axial thickness of the first elastomeric rings in the first stack is greater than a combined axial thickness of the second elastomeric rings in the second stack.

12. The cushion tool of claim 10, wherein an outer peripheral surface of each of the at least two first elastomeric rings has a contoured profile selected to relieve induced strain when the resilient compliance member is further compressed.

13. The buffer tool of claim 10, wherein the first stack further comprises first shims alternating with and bonded to the at least two first elastomeric rings, and the second stack further comprises second shims alternating with and bonded to the at least two second elastomeric rings.

14. The cushion tool of claim 10, wherein the first elastomeric ring is configured to bulge and fill a free volume between the resilient compliance member and the housing under a large load, and the second elastomeric ring is configured to bulge and fill a free volume between the compressive compliance member and the housing under a large load.

15. The cushion tool of claim 14, wherein the first elastomeric ring is configured to bulge and fill a free volume between the resilient compliance member and the mule shoe adapter portion under a large load, and the second elastomeric ring is configured to bulge and fill a free volume between the compressive compliance member and the mule shoe adapter portion under a large load.

16. The buffer tool of claim 1, wherein the drive washer includes an internally threaded surface, the mule shoe adapter includes an externally threaded surface, and the drive washer is coupled to the mule shoe adapter by engaging the internally threaded surface with the externally threaded surface.

17. The buffer tool of claim 16, wherein the drive washer includes an inner tapered surface adjacent the inner threaded surface, the mule shoe adapter includes an outer tapered surface adjacent the outer threaded surface, and the inner tapered surface mates with the outer tapered surface when the inner threaded surface is engaged with the outer threaded surface.

18. The damper tool of claim 1, said damper tool having a selected precompression under all load conditions, said selected precompression being divided between said rebound compliance member and said compression compliance member into said first precompression and said second precompression, respectively, wherein an initial value of said first precompression is at least 90% of said selected precompression.

19. A downhole tool string, comprising:

a Universal Bottom Hole Orientation (UBHO) joint, inside which a mule shoe is arranged;

a snubber tool disposed within the universal downhole oriented sub, the snubber tool comprising:

a mule shoe adapter coupled to the mule shoe;

a universal downhole orientation (UBHO) adapter mounted on the UBHO joint;

a resilient compliance member having a first stiffness and a first precompression, the resilient compliance member configured to maintain at least a portion of the first precompression under an external load of the bumper tool;

a drive washer disposed between the resilient compliance component and the compression compliance component and coupled to the mule shoe adapter, the drive washer configured to selectively apply further compression to the resilient compliance component and the compression compliance component in response to an external force acting on the mule shoe adapter.

20. A method of reducing vibration in a downhole tool string having a mule shoe, comprising:

coupling a bumper tool to the mule shoe of the downhole tool string, the bumper tool comprising: a resilient compliance member having a first stiffness and a first precompression and configured to maintain at least a portion of the first precompression under an external load of the bumper tool; a compression compliance component having a second stiffness greater than the first stiffness and a second precompression less than the first precompression and configured to maintain at least a portion of the second precompression under an external load of the bumper tool; and a drive washer disposed between and in contact with the resiliently compliant component and the compressively compliant component;

receiving a force exerted on the mule shoe at the drive washer of the snubber tool; and

further compressing one of the rebound compliance component and the compression compliance component of the bumper tool by movement of the drive washer in response to the received force.